It's a Tool script, not a Comp script. It must therefore be located in Scripts/tool and then run by right-clicking the tool in question and choosing it from the Script section of the context menu. Or you can do what you've done to run it as a Comp script.

The timeline is a strange hybrid at the moment. You can right-click/animate, publish etc in Fusion clips, but they are all seperate compositions, so you cannot connect various attributes/values to each other. On the other hand, it appears that there are some timeline/clip related scripting options, so in theory you should be able to iterate through all the Fusion clips and collect a couple of values that could be manipulated. At least, that's what my layman's brain thinks.